1. Field of the Invention
This invention relates to a retrieval system for retrieving of an object within the vasculature of the body, and more particularly to a retrieval system which may be used in the removal of a medical device within a blood vessel. More specifically, the retrieval system may take the form of an embolic coil retrieval system to be used in the removal or repositioning of embolic coils within the brain.
2. Description of the Prior Art
For many years physicians have been placing various devices within a blood vessel of the human body in order to treat an aneurysm or to occlude a vessel by promoting thrombus formation. Such devices include dilatation balloons, liquid medications, stents, and embolic coils. Embolic coils may take the form of helically wound coils, randomly wound coils, coils wound within other coils, or many other coil configurations. These coils are generally formed of radiopaque metallic materials, such as platinum, gold, and tungsten, or alloys of these metals.
U.S. Pat. No. 6,179,857 entitled, “Stretch Resistant Embolic Coil with Variable Stiffness” discloses one such embolic coil design. The coil disclosed in this patent is a helically wound coil in which various combinations of adjacent turns are spot welded together to create a stretch resistant coil of a preselected flexibility. U.S. Pat. No. 6,183,491 entitled, “Embolic Coil Deployment System with Improved Embolic Coil” discloses another coil configuration which shows an embolic coil having a relatively flexible proximal portion which resists stretching.
Instead of placing an embolic coil within an aneurysm to prevent the flow of blood, a stent may be used to treat an aneurysm. U.S. Pat. No. 6,267,783 to Robert P. Letendre, et al discloses one such stent. The stent disclosed in this patent is a self-expanding stent which may be placed within the parent vessel of the aneurysm and positioned over the mouth of the aneurysm to block the flow of blood. Another stent aneurysm treatment device is disclosed in U.S. Pat. No. 6,361,558 entitled, “Stent Aneurysm Treatment System and Method” and assigned to the same assignee as the present application. That patent discloses vasculature stents of various configurations which may also be used as aneurysm covers for occluding, or partially occluding, aneurysms located at various positions along blood vessels.
In certain instances an embolic coil or stent must be removed from the vessel and either repositioned or replaced. Furthermore, a stent may require replacement because it has outlived its useful life. One known procedure for embolic coil or stent removal is surgically removing the device from the vessel. This method however can be time consuming and traumatic to the patient. The development of flexible medical instruments has made it possible to remove embolic coils and stents using minimally invasive surgical procedures. U.S. Pat. No. 5,098,440 entitled, “Object Retrieval Method and Apparatus” and assigned to the same assignee as the present invention discloses one such device. This patent discloses an apparatus which captures a stent with two criss-cross wire loops. These wire loops slip over a stent, and when the ends of the wires are retracted the loops tighten down on the stent. The stent is captured and withdrawn into a guide catheter.
U.S. Pat. No. 5,217,484 entitled, “Retractable Wire Catheter Device and Method” discloses another apparatus which may be used to retrieve or adjust the position of a deployed vaso-occlusive device. This patent discloses a catheter device having a multi-jaw clamp. When the clamp is placed over a vaso-occlusion wire, a pusher wire is retracted to close the jaws of the clamp thereby capturing the wire for retrieval. A spring jaw medical instrument is disclosed in U.S. Pat. No. 5,782,747 entitled, “Spring Based Multi-purpose Medical Instrument.” That apparatus, used for capturing an intravascular object, has a variety of jaw structures including a configuration having opposing serrated surfaces for crushing an object and a configuration having a closed loop jaw suitable for grasping an object.
Also, U.S. Pat. No. 5,840,043 entitled, “Jaw Assembly for an Endoscopic Instrument” discloses a retrieval apparatus. This patent describes an instrument which includes a jaw assembly having cups with radially arranged teeth. The jaw assembly with this knife-sharp rim is actuated by a push/pull wire which allows physicians to obtain a multiple sample bioptome.